Hello Hazzar,
There are plenty of third party sites that claim to have data for cars, but none of them are complete or should be used as being gospel. Several significant errors have been found in them. The problem is you don't know which figures are inaccurate. Kerb weights are notoriosly difficult to accept.
You should always use the data that comes with your car and on the V5 document, or if in doubt seek confirmation from the vehicle manufactuer against its specific vin plate number.